Dentin is the substance between enamel or cementum and the pulp chamber. It is secreted by the odontoblasts of the dental pulp. The formation of dentin is known as dentinogenesis. The porous, yellow-hued material is made up of 70% inorganic materials, 20% organic materials, and 10% water by weight.
Medical Definition of metaplasia. 1  1: transformation of one tissue into another metaplasia of cartilage into bone. 2  2: abnormal replacement of cells of one type by cells of another.
Tissue evidence of carcinogenic factors at work. Metaplasia: an initial change from normal cells to a different cell type (such as chronic irritation of cigarette smoke causing ciliated pseudostratified epithelium to be replaced by squamous epithelium more able to withstand the insult).issue evidence of carcinogenic factors at work. Metaplasia: an initial change from normal cells to a different cell type (such as chronic irritation of cigarette smoke causing ciliated pseudostratified epithelium to be replaced by squamous epithelium more able to withstand the insult).